Currently, most commercially liquid crystal displays in the market are backlight type liquid crystal display devices. White light LEDs (Light Emitting Diodes) are generally used as backlight sources. The most common white LED is a blue light emitting die with a yellow yttrium aluminum garnet phosphor powder. In case that the LED with a yellow phosphor material is used with a liquid crystal panel, the color saturation is low. The display color gamut is generally about 72% NTSC (National Television System Committee) and the display color is not bright enough. In order to improve the color saturation, the yellow phosphor powder can be changed to a red green (RG) phosphor powder. However, this method can only increase the color gamut by up to about 25% and fails to meet the new BT.2020 color gamut standard (equivalent to 134% NTSC).
At present, what can realize 80% of the BT.2020 color gamut standards is the quantum dot technology, i.e. the LED having a blue light emitting die plus green quantum dots and red quantum dots. However, the thermal stability and blue light stability of the quantum dots are poor and can easily react with water and oxygen after light exposure to cause the defects occur, resulting in reduced efficiency of the material excitation or even failure and seriously affecting the service life of the LED. Meanwhile, the quantum dot material is expensive and is mostly composed of heavy metal-containing substances. The use of large amount of the quantum dots can cause environmental pollution and increase the cost. Therefore, there is an urgent need for a highly reliable, high color gamut and low-cost light emitting diode.